Load Development for the Mossberg MVP .308 WIN

Last April, I posted a review of Mossberg’s MVP-LRT, a sixteen inch barreled, bolt action, magazine fed “tactical” rifle. It had just about everything going for it to meet 90% of my rifle needs. Chambered in a robust enough short action cartridge, it could feed from a twenty-round magazine, and with its barely legal sixteen-inch threaded barrel, it was a great host for a silencer.

Truth be told, I thought for sure that I’d found my perfect hunting/run and gun/have fun rifle. The only nagging issue: accuracy.

No matter what I threw at the lil’ Mossy, it just never really performed better than about 1.1 MOA and that was only with fancy (expensive) match ammo. Most everything else produced 1.5 – 2.5 MOA. Given that, I figured it would be a fun rifle to work with for an ongoing series on the possibilities of hand loading. And given that Nick had gotten away from rolling his own when he moved to Austin, I had a lot of free components to work with.

There are only four components to a loaded cartridge…and roughly a million variables to control for. To ease my burden some, I elected to raid the RCBS catalog — and my bank account — to acquire a Rock Chucker Supreme, a Chargemaster, and the appropriate set of dies. I also used some credit card points to purchase a five-pound bag of stainless steel pins and a rock tumbler so I could effectively clean my brass.

Part of the gift box from Nick included a trimmer that worked with my cordless drill. At the time of this project, I used a buddy’s Hornady Lock n Load OAL Gauge, but I’ve since picked up my own.

Fresh off watching “Reloading from A-Z“, I set about putting together a reloading plan. First up was aggregating the components. I’d had the forethought to start collecting my brass over the prior months, and I had amassed a few hundred pieces of once-fired Federal brass marked “FC 308” from Federal Gold Medal loads. Given how consistent Federal Gold Medal is in most rifles, I figured their brass must be pretty good, and the price was certainly right.

I had originally wanted to use Federal primers, but the supply everywhere I looked was down to zero. Wanting to set myself up for success in case this whole reloading thing actually worked out, I chose to purchase a few hundred CCI 200’s at the local Gander Mountain. A word to the new reloader: unless you’re planning on ordering in bulk, buying locally will save you a fortune on hazmat fees. This applies for both primers and powders.

Nick’s gift box also included several hundred Hornady 150 gr. FMJ projectiles from his 300 BLK reloading days. The 150 FMJ isn’t the slickest bullet out there, but they certainly were reasonably priced (free). Assuming they performed well, that particular projectile is still very affordable at less than 20 cents per bullet when purchased in bulk. Given that this rifle only has sixteen inches of barrel, I also wanted a lighter bullet that I could push fairly quickly.

Which brought me to powder. A friend had gifted me a slightly depleted pound of RL-15, but my reading on the internet indicated that RL-15 was quite temperature sensitive. That was no good for my uses, so I punted it from contention. I had heard great things about Hodgdon Varget so I picked up a pound and decided to work up a load.

With all the components and a rifle, I set off to take care of the first order of business – length. I used Hornady’s Lock n Load gauge to establish the absolute longest overall length I could load to because somebody on the internet (see a theme here?) told me it was important for precision reloading. Following that line of logic, I subtracted .050″ from that maximum measurement, again because I read it on the internet, and set that as my base to ogive measurement.

For this particular rifle and load combo, that measurement was 3.140″ which correlated to an overall length (OAL) of 2.710″. Hornady’s book recommends loading to an OAL of 2.700″ for this bullet, so I felt confident that I was roughly in the ballpark.

The next step was to put together a list of charge weights of Varget to establish a broad range of weights that might lead to a winner. Early in my reloading journey, I told a friend that I always started at the book minimum and worked my way up in 3/10 grain increments to the maximum. He asked me why I loaded down to minimum to which I replied, “To find an accurate group!”

“So if you find a half-minute shooter, but it chugs along at 200 fps slower than a group that gives you one minute accuracy, are you going to stick with it?” That’s good advice and makes sense as slow loads aren’t really that much fun to begin with.

Hornady lists 44.9 grains of Varget as their max load for the 150 FMJ. They also indicate that their twenty-two-inch 1:12 test barrel showed 2700 fps with that combo. I started 2/10 grain below that because at the time I worried about my ability to identify pressure signs, and I’ve grown quite attached to most of my facial features.

Starting at 44.7 grains and dropping down by 3/10 of a grain at a time, I established 10 loads that I wanted to test. They ranged from 42.0 – 44.7 grains. I carefully measured out five charges at each level, poured it in my trimmed, chamfered, deburred, primed cases, and corked it with a 150 gr FMJ loaded to 3.140″ on my Hornady OAL gauge. I strapped an appropriately large optic to the Mossy and headed out.

At the range, I put up the targets you see above, and shot five-shot groups starting at the lowest charge, and working my way up checking for pressure signs along the way. Having made it safely through my load workups, I packed up my targets, and headed home to process them in OnTarget.

I plugged all of OnTarget’s data into Excel and was pleasantly surprised to see a number of groups below one minute. In fact, nearly every round I had put together shot better than factory ammo, essentially validating the entire reason I’d taken on this project. I’d been able to roll my own that were more accurate than what I could buy from the factory. What fun!

Looking at the horizontal, vertical, and max spread for each group, I targeted the 44.1 and 44.4 grain charge weights as being worth a second look. Both showed fairly good accuracy at the higher end of the charge weight spectrum while still maintaining zero signs of pressure. I loaded up ten rounds each at 44.1, 44.2, 44.3, and 44.4 and headed back to the range.

There, I fouled the barrel with five rounds of Gorilla 175 which shot a 1.2 MOA group, then commenced the same five-shot grouping test I’d done previously, working from lowest to highest. The 44.1 grain load, incorrectly marked on the target above, turned in a just barely sub-minute group, with 44.2 stacking five pretty close to each other for a .638 MOA group. 44.3 and 44.4 grains, again both incorrectly marked, fell apart and I elected to put together the following load.

Case: Federal Gold Medal 1X fired – headstamp FC 308

Primer: CCI 200 LR

Powder: Varget

Weight: 44.2 grains

Bullet: Hornady 150 FMJ

OAL: 2.710

Base to Ogive: 3.140″

With my established load, I used my MagnetoSpeed to chronograph the remaining five loaded rounds at 2,591 fps with a SD in the low teens. The remaining loads were burned up in practice.

I purchased Varget for $26/lb plus tax so this charge weight works out to be ~$0.17 per cartridge. Hornady’s 150 FMJ can almost always be found for less than $0.20 per and CCI primers are about $0.035 per, so my component cost was around $0.40 per cartridge exclusive of brass. In my case, brass was “free” in that I otherwise would have thrown it away. Brass prices for .308 range from $0.20 to $1.00+ so it’s one of the most variable costs besides the projectile. I police my brass and push a fairly moderate load so I’ve been able to get several reloadings out of this FC 308 brass.

I used this load and rifle for the Pecos Run n Gun where I placed well given the circumstances and while I had some misses, they were all shooter related. I successfully engaged targets out to 400 yards, and while I certainly had problems with this ammo going off, it was all related to a dirty firing pin on the Mossberg.

Since this was my first attempt at rolling my own from start to finish, I did a lot of things that I’ve later come to regret. First, I never loaded up any rounds beyond maximum. It’s very possible I could have put together an accurate load at a much faster velocity that wouldn’t have had pressure signs. Nearly 2600 fps is no slouch, especially in a 16-inch rifle, but speed is speed, especially in a lighter bullet weight.

I also failed to chronograph anything until I’d established an accurate load. Luckily for me, 2600 fps was a pretty good place to be, but had that not been the case, I would have burned up a lot of powder, projectiles and time putting together a load I’d never use in real life.

On that note, loading up ten different charge weights is fairly wasteful. I was lucky in that my brass was essentially free as were the bullets. .308 WIN isn’t the cheapest thing to load for, but it’s still fairly affordable. Loading for my 7mm Magnum has shown me that being judicious in the load workup process can mean money saved for other projects.

Finally, this method of shooting one five-shot group per charge leaves the door wide open for shooter-induced errors to drive the reloading process in a less-than-perfect direction. As I’m hardly a world class shooter, I don’t have the confidence to state that a shot that lands wide is my fault or the gun’s.

Having used this process with another rifle, I found that a load that shot one amazing group (.25 MOA) on one day consistently turned in 1.0 – 1.5 MOA loads on a lot of other days. I still believe that I ended up with a successful combination for this rifle as I regularly shot sub MOA groups with it, but I believe that was due more to luck than skill.

comments

I’m not so sure that every overpressure round will show signs… so I’d probably stay away from that line of thinking, going over the max just because the shells don’t show overpressure. But that’s just me.

That load data from Hornady is conservative. If you compare it to other books, it’s a significantly lower max charge weight (take a look at http://www.hodgdonreloading.com/data/rifle). I generally prefer to have three different printed manuals of data. I use a LOT of Varget in particular, and a lot of Sierra bullets, so that’s two sources, and Lyman is good old school to use as a third.

If I have another printed source that says I can go higher, then so be it; that’s data that says the first source is NOT the maximum. But based on a single source, that’s based on instrumented chambers to determine pressure, I’d personally stick with the printed data.

I can’t help but wonder if you wouldn’t be better served by a quality match bullet and an OCW development series at 200/300 yards. You put a lot of effort into that load – great article, good articulation of why you did what – but bullet selection MATTERS. Especially with a short, stiff barrel like that, where your vibration nodes are going to be “wider”, a few tenths of a grain higher or lower with a stick powder (like Varget) won’t matter much. Certainly not NEARLY as much as a quality bullet (charge weight, not barrel). Your rifle shoots crap bullets under 1 MOA, with good heavy bullets you might get to 1000 yards with that shorty and hit what you’re aiming at!

Additionally, emphasizing net component cost per round misses the huge time sink – even a writer’s time isn’t free 😉 I don’t generally load anything but premium bullets in either pistol or rifle, if I want plinking fodder I can buy it cheaper than I can make it especially if I factor in time. Making ammo I can’t buy is my goal, in that it shoots better than I can buy in my guns OR in the case of non-lead hunting ammo is a combo no one loads commercially (less of a problem now than in 2008). I can handload ammo for my High Power rifles for a nominal $0.55/rd, but since neither one shoots the equivalent FGMM worth a darn at $1.50/rd, it’s irrelevant what the cost comparison is. Good thing my 03-A3 liked the test ammo I bought!

I won’t step in the wife avoidance thing, but generally speaking, accurate ammo and rifles are better for practice than not. And while I might have a harder time ringing steel at 750 yards with this vs a 175 SMK, most of my shooting is 250 yards and under and this flies close enough to be effective on 10″ steel plates and IPSC torsos.

At another dime or so cheaper per round vs. the 175 SMK, I do get the opportunity to practice a bit more for the same money.

I agree, bullet selection is the most important variable. Think about it. The bullet is spinning around 200,000 rpm coming out. If it’s not perfectly balanced it’s not going to fly the same direction each time.

I’ve been researching load development a lot because I’m looking at starting to do the same thing- grab a reasonably-priced .308 and start throwing lead at 300-600yd targets. So, I sound smarter than I actually am on the subject and I’m legitimately looking for your answer, not trolling/criticizing.

Anyway- is there a reason that you decided to just go with “smallest group” as your metric for charge weight, as opposed to doing something like an OCW workup or ladder test to compare vertical point of impact stability across different charge weights? That would save you a bit of time when loading in the long run, as well, due to being able to use a powder measure and not necessarily wait 15 seconds for the Chargemaster to finish dispensing every round manually.

Well honestly, it was all I knew! I’ve since researched ladder testing and performed some of my own and found it to be quite a bit better at a.) finding an accurate node and b.) not using up a bunch of components.

Does it generally shoot nice and tight and then widen out or shift it’s POI after 4-5 rounds?

I have a Mossberg 100 ATR in .243 that does that. Shoots dead on but the end of the second group goes to crap. At first I thought it was me but the issue is repeatable after letting her sit for a bit and it happens to other people too. I think it’s just a poor barrel.

From what I understand, what you are describing is an effect from the barrel heating up after multiple shots. Let your rifle cool down adequately after each group. And you might be limited to more like 3-shot groups.

Also from what I understand, that is not a “poor” barrel, it is what you get in an inexpensive rifle.

Oh, make sure to leave the bolt open and the barrel pointing into the wind between shots to cool it down as much/quickly as possible between shots.

The place I shop for projo’s has 168 gr boat tail match bullets for $275/K. AMax bullets are the same price.
I’d be interested in the twist rate of your barrel. It might be more suited for a heavier bullet.

According to mossbergs website. Twist is 1/10. It was my understanding a heavier bullet was better for it. I have the scout version of this rifle and i shoot 168gr bullets preferable. Mine are factory amax. Dont have the time/space to reload

– Is your sizing die just bumping the shoulder, or full-length sizing the brass? If you’re not shooting hot loads, you should be able to just neck size and bump the shoulder by 0.002 or so, leaving the rest of the case alone – if you’re going to use these loads in only this rifle. If you plan on shooting your reloads in a semi-auto rifle, you’ll need to full length size to get reliable chambering.
– do you know what your leade is? ie, how far is your bullet “jumping” out of the case before it engages the lands? Some .308’s want to be set with the bullet actually in the lands (with reduced loads) to get them to group tightly, some will tolerate the bullet being 0.050″ off the lands. It depends on the barrel and chamber. Many BR shooters play with the bullet jump quite a bit before they start searching for the optimum charge weight or velocity.
– How are you seating the primers? I like to use a hand priming tool, so I can feel how a primer is seating.
– Are you cleaning the primer pockets to get uniformity in seating?
– Are the primer holes all uniform? You don’t have to drill them all out to a uniform size at this point, just visually inspect that they’re not damaged or enlarged from a decapping operation gone wrong.
– You’ll find that igniting a load as uniformly as possible pays dividends. The match primers to use will be something like Federal 210M’s, or CCI BR-2’s.
– Varget is a good powder, there’s absolutely nothing wrong with it. I buy and stockpile lots of it. It is less temperature sensitive than other powders, but before you write off other powders… just how much temperature swing are you anticipating? If you’re not developing your loads in the northern climate in winter, and then shooting in the Texas summer, you might not have as much MV variability as you think with some of the more “sensitive” powders.
– I’ve seen .308-type cases (ie, the .308 and everything based off of it) can sometimes like different powders in different rifles. Some of the other powders I’ve heard customers claim were good in their rifles: IMR 4350, W-748, BLC(2), IMR 4064, Re15. Re15 is known to give higher velocities at accurate load levels than some other powders.
– A better bullet, preferably one of the new all-copper match pills helps in some cases. Sierra has very good match grade pills. Berger is the choice of lots of benchrest and F-class shooters.
– Sometimes, you need to play with different bullet weights to see a rifle group. Some rifles really don’t like “light” bullets, some rifles don’t twist tight enough for the heavier pills. The best accuracy pill in .308’s for decades was the 168 Sierra Match King. Now lots of guys are going to the 175gr match pills. There are match-grade 155gr pills for the Palma shooters that work well in .308’s. There’s plenty of choices to play with.

I like to use a Lyman reloading book, because they call out the most accurate load they find for a powder/bullet weight combo as well as starting & max loads. I’d also use a balance or known good electronic scale to double-check the charge weights from the Chargemaster.

The two components I find make the most difference for the time & money are primers and bullets. I can make crappy cases into good cases, and you can play with your powder load to make a load from just about any powder perform better. You can’t make your own primers, and the difference in bullet quality between the run-of-the-mill bullets and the best bullets has become quite pronounced.

Example: I have a .270 Winchester, post-64 Model 70 that groups 2″+, no matter what I did to try to make Nosler Partition bullets group in it. Didn’t matter whether I was loading 130’s or 150’s, didn’t matter the powder, didn’t matter the OAL, length to lands or primer… I could not get it under 2″ at 100 yards.

The first load I tried with Barnes 150 grain TSX’s, loaded to book OAL, grouped 0.75″ with a five-round group. The Nosler Partition has been a great bullet for decades – but there’s now better pills available.

Spot on as usual. I use 4350 in my loadings mostly because with a powder trickler and an electronic scale, I can be very precise in my powder.
BLC(2) meters nicely out of a thrower. I use it in my Dillon 650 for mass loading plinkers.
Totally agree on bench or match primers and the flash holes. I also only use a hand primer for my good ammo. I’ve been able to discard some brass because the primer just slid in with no friction.

I prefer the same charge measuring method you’re using Tom. I use a throw for all but the last 0.1 to 0.2 grains, then trickle the rest in.

The longer the stick shape on the powder, the more margin I’ll leave to trickle after a throw. Stick rifle powders can have issues in metering on a throw as the throw breaks/cuts grains of powder. Some rifle powders have two versions – the long stick and the short stick. One such powder is IMR 4831 – you have the original long grain powder, which didn’t meter as well through a powder throw, and the new variant, “IMR 4831SC” or “short cut,” which meters better, but not as well as ball or flake powders do.

You people with your fancy electronicals. I still churn out all my rounds on two single stage presses. I manual scale measure every round. My Brown and Sharpe calipers measure every case length and every over all length. I do all my case prep with manual tools. Yes, that includes my plinking ammo as well. Yup, I have a sleeping disorder. But reloading for an hour or so a night puts me right down.

If I were in another state, I may reconsider temperature variation as a factor, and having a summer vs. winter load is perfectly reasonable. After all, most of my rounds don’t last 6 months anyway.
But the weather here is just ridiculous. During the last week of regular white tail season this year, we saw the temperature at our farm go from 75f to 12f, in barely 72 hours. It hit 80 in January, but we will certainly have at least one more hard freeze before Easter.
And then there is the load you develop with your .22-250 for some song dogs on a nice 55 degree April morning, only to finally get out in August when it’s 112.
The highest recorded highs and lowest lows in Texas are a full 140 degrees apart.

I like the article a lot. I too am working up loads for a 308. Mine has a longer barrel (26″ bull) with a 1 in 12 twist. It shoots dead on at 100 with 168 FGGM. I plan on cloning that and I zeroed to it as you can find it most places. I plan on developing a better load but my scope has target turrets and I can do pre adjusts. One powder that so far rivals Varget in my loads in AR Comp. It seems temp stable as well. I have a good selection of powders from loading my 5.56 but some are a lot better than others. BTW, I also got some SS pins and may not use walnut or corn much anymore. The brass does shine. Great article and I hope to see some followups as your testing continues.

Federal Brass is the same weight and volume as US GI Brass, it has been suggested that starting powder weight should be backed off 2 grains from max! so if you shot Maximum charge you would be already 2 grains over charge.
Be careful taking charge weights out of books with different brass, case strength and volumes are different!
also changing primer brands can give interesting results! Once changed a primer from Remington 9 1/2 too CCI 200
with a group consistently 1′ higher than Rem groups. A friend makes 3 samples and shoots for groups once he finds 3 good groups he then goes to 5 cartridges each, then 10! speed of bullet is minor if you can’t hit with it, plus why beat your shoulder up with extra recoil, especially if shooting a hundred or so rounds ad day from different calibers. besides my targets really don’t care if they get hit with a .001″ group or a 1.00″ group! or really care if it is putt putting or zipping along, IMR XBR 8208 is a great powder for 168gr and CFE 223 pushing a 175 grain

Excellent post. I have been toying with the idea of getting into reloading, and this post, and the comments that follow, confirm what I long suspected: I don’t have the time to devote to doing it right. Maybe when I retire….

I recently put together a cheap match load with the 75 gr. BTHP that regularly shoots 3/4 MOA at 2600 fps out of my 16″ AR. I simply haven’t found a factory load that does that.

You probably have more time than you give yourself credit for. If you’re diligent about notating your progress, you can break it up into 15-30 chunks of time. Ex: On Tuesday, I went shooting after work and created about 150 pieces of 308 and .223 brass. I spent 15 minutes depriming the .308 and tossed everything in my SS media tumbler, set it to run for 45 minutes while I made dinner, and then dumped the brass to dry overnight before I went to bed.

On Wednesday, I spent 30 minute resizing the 308 and 223 and then set it aside for trimming/chamfering/deburring. You see where I’m going with this. Just plan your time out and it’s totally possible.

Great article.
Don’t get into the game of chasing velocity. The terminal performance is not worth the wear on your gun, your body, or your pocket book.
Take, for example, the difference between the starting load and maximum loads for Varget with a 168gr SMK .308Win. That’s about 200fps on a true rifle length barrel. Wow! 200fps you say. What does that mean at 1,000 yards? A whopping 48ftlbs of energy. Forty. Eight. It means less than the temperature and elevation. Your target, even if it is a live one, won’t know the difference between 48ftlbs.
Now, the difference of even half a minute of angle loss at 1,000 yards is enough to be inside or outside of the vitals, and that does make a difference.
Just fast enough, but accurate as it can be, is my guide.

hmm I had the Predator version, i thought it shot wonderfully. and the only ammo I ever put through it was American Eagle and Monarch and was getting 1.5-2 MOA at 200 yrds. that was good enough for me, i don’t see the point it going for much tighter. I only had a crappy 4 mag fixed scope so couldnt got out much further than that. for a $500 rifle i thought it was well worth it. but im not any kind of bolt guy by any means.

Reloading rifles is much more tedious than pistol. I have pretty much decided I will most likely buy bolt gun ammo and just reload pistol and blackout myself. i dont shoot alot of bolt guns and dont really care for the whole sub MOA dragon chasing either.

If you’re reloading for a semi-auto rifle, or for guns other than the one the case came out of, you’ll generally need to
1) Resize the case, using lube
2) Clean the lube off the case
3) Trim the case to length
4) Chamfer the case mouth.

You can usually avoid all of the above if you’re reloading for a bolt gun and only for that specific bolt gun. And yes, you can avoid that whole mess with a semi-auto but it’s not recommended. Perfectly sized fire-formed brass works fine until the chamber gets dirty.

The Load Data compiled in each reloading manual is a general guide and the data is specific for that particular test rifle utilizing that specific brass (the Mfgr.) the specific primer used, specific bullet (mfgr., style, and weight) and the specific OAL (i.e. seating depth) with that bullet listed. ANY change of the components results in a whole new ball game. If using Hornady bullets, use Hornady’s manual, if Sierra, sierra’s, etc. All manuals recommend STARTING load development by reducing powder charge weights by Ten Percent and starting at the BOTTOM of the powder charge weights to account for variations in case volume, chamber and barrel dimensions, etc. Exceeding recommended Max. powder charge weights is courting disaster and IMHO, irresponsible unless you have the means to measure chamber pressure, such as an Oehler 57.

Excellent article! Just got a Ruger American in .30 06. Love the gun, relatively light and a really nice trigger. I purchased 12 various types of ammo from Wolf Steel case 145 & 168 FMJ to one box of 168 gr Federal match, and everything in between 150 to 180 Gr, Winchester, Federal and Hornady. It was an interesting day at the range. I will say that this is a remarkable rifle for $340! The Wolf 168 gr shot really well, 2″ @ 100, for what is was and Hornady 150’s were the worst 3″. Winchester SuperX in 150 and 180 were sub MOA at 100 yards. The rest were in the 1 to 2 inch, all 3 round groups. Just a first time outing to get a feel for the new toy.

My big question is if I want to get back into reloading?! One part of me says yes, but my other half asks why? This new rifle shoots factory really well and my FNAR shoots factory as well or better. Even the Wolf shoots better than what I remember factory shot back in the 60’s. Now when shooting the FNAR I tend to burn up a lot more ammo (those 20 rnd mag dumps are just too much fun). But I don’t think I can reload as inexpensively as I can purchase Wolf 35 – 40 cents per round. Commercial ammo is so good compared to when I last reloaded back in the ’60’s I’m just not able to convince myself to do it. Yet.